Airplane propeller



Sept. 30, 1947.

R. M. JOHNSTON AIRPLANE PROPELLER Filed March 25, 1943 s Sheets-Sheet 1 I::: l: I. 1::

AIRPLANE PROPELLER Filed March 25, 1945 3 Sheets-Sheet 2 Patented Sept. 30,1947

UNITED STATES ATENT OFFICE 2,428,225 AIRPLANE PROPELLER Robert M. Johnston, South Charleston, w. Va. Application March 25, 1943, Serial No. 480,530

1 Claim.

This invention is a variable pitch and variable diameter propeller for airplanes.

The high efliciency of modern airplane propellers in level flight at low altitudes is well known in the art. It is well recognized, however, that there is a need for improved performance of airplane propulsive systems which increases to the imperative when maximum weight-carrying, maximum range, maximum climb for pursuit planes, and maximum speed and maneuverability at high altitudes, for war or peace are considered. Air at 28,000 feet is only .4 as dense as the air at sea level. Therefore, an engine operating at that altitude would only develop .4 of

its sea level power pressed to almost sea level density before being driven into the engine. The use of superchargers has greatly improved engine performance at high altitudes but there has not been a full corresponding improvement in propellers to operate in the rarer parts of the atmosphere. For maximum efficiency at such altitudes approximately two and one half times the volume of air must be handled in the propeller slip stream to achieve the same thrust in pounds as at sea level.

One of the important objects of the invention is to provide a propeller which will be capable of taking full advantage of stratosphere flying without sacrifice of performance at lower altitudes. A further object is to provide a propeller capable of improved performance in safely picking up heavy loads of any kind. A further object is to provide means for increasing the thrust of the propulsive system at take off, in climbing after take level flight.

The invention will be hereinafter fully set forth and particularly pointed out in the claim.

In the accompanying drawing Figure 1 is a top plan view of a four bladed variable pitch and variable diameter propeller constructed in accordance with the invention, the spinner being shown partly broken away to illustrate essential parts.

Figure 2 is a rear elevation of the structure illustrated in Figure 1.

Figure 3 is a detail sectional view of the actuating mechanism adjusting the propeller diameter and pitch, respectively.

Figure 4 is a longitudinal sectional view illustrating one form of mechanism for effecting the radial diameter adjustments of propeller blades, and also for effecting the variable pitch adjustments of the blades.

Figure 5 is an end elevation of the structure if not supercharged, or comoff, and at high altitudes in illustrated in Figure 3, showing the gear arrangements.

Figure 6 is a sectional view on line ure 4.

Figure 7 is a view similar to Figure 4 illustrating a modified form of adjusting means, applied to a four blade propeller.

Figure 8 is a view similar to Figure 7 showing the blade adjusting means applied to a two blade propeller.

Referring to Figures 1 and 2 of the drawings, 8 designates a conventionally shown propeller spinner which may be of any well known construction, and connected to the propeller shaft P in the usual way. Located axially within the spinner S is a housing H, which contains two rotors R and R respectively, which may be of any desired type. For purposes of illustration, and without intent to limit the invention in this respect, these rotors are shown as consisting of electric motors, which may be controlled from the instrument board in any suitable manner well understood in the electrical and airplane arts. The motor R drives a shaft r and controls the longitudinal movements of the propeller blades in order to vary the effective lengths thereof. The motor R drives a shaft r through suitable reduction gearing conventionally indicated at B and controls the rotative or pitch adjustments of the respective blades.

The structure shown in Figures 1 and 2, is a four blade propeller, each blade B being slidingly mounted in a guide barrel GB radially arranged within the spinner S. The motor shaft 1* is proa drive gear Ill which meshes with pinions H and I2 secured to worm shafts i3 and I4, which extend through the housing H and operate on the outside thereof. The worm shaft I3 is provided with a worm I5 of any desired construction meshing with a worm wheel I6 on a screw shaft i1. It is also provided with a second worm I 5a meshing with a worm wheel Ilia on a screw actuator I "Ia. In a similar manner the shaft i4 also extends through the housing and operates exteriorly thereof, being provided with a worm l8 meshing with a worm wheel I9 of a screw shaft 20, and a second worm I8a meshing with a worm wheel I9a on another screw shaft 20a. The screw shafts are connected to the propeller blades, so that upon. rotation of the screw shaft the blades are simultaneously moved inwardly or outwardly with respect to their guide barrels.

The shafts I1, Ha, I9 and I9a are screw shafts connected to the respective blades B. More spe- 6-6, Figbearings 32.

'movable with the .of the figure.

3 cifically the means by which the blades and the screw shafts are operatively connected may be either of the forms illustrated in Figures 4, 7 or 8, to be later described, The arrangement is such that upon energization of the rotor R, the blades B will be moved inwardly or outwardly, depending upon the direction of rotation of the motor.

As shown in Figures 1 and 2, the driven shaft 7'' of the transmission R is provided with a beveled pinion 25 which meshes with complemental pinions 26 and 2'1, connected with rotatively mounted members to which the inner ends of the respective blades are connected. These members may be of either of the forms illustrated in Figures 4, '7 or 8.

The structure illustrated in Figures 4, and 6 is primarily designed for a two blade propeller, but obviously by duplication, the same construction may be applied to a four blade propeller such as illustrated in Figures 1 and 2. Referring to said Figures 4, 5 and 6,a head 30 is slidingly mounted for rectilinear movement within the guide barrel GB, said head being internally threaded to engage a set of screw threaded shafts 3!. Three of said shafts are shown, each mounted in suitable ball The bearings at one end only are illustrated, it being understood, however, that the other end of each screw shaft is supported by a duplicate bearing 32. Rotatively mounted in bearings 33 within the head 30 is the tubular innerend of a blade B. The saidbearing 33 is head 30, being connected thereto by the threaded ring 33a, so that the blade B will conform to the rectilinear movements of the head 30 and thereby produce the desired bladelength adjustment. In the section illustrated in Figure 4, the mechanism for actuating but one blade is shown, it being understood that the other blade which is shown at the lower part of the figure is operated by a mechanism which is a duplicate in all details shown in the upper part Rotative movement of the screw shafts is effected by a drive gear-'35 meshing with pinions 36 carried by the respective screw shafts, said drive gear being mounted upon a hub which also carries a worm gear 311. Referring more particularly to Figure 5, it will be observed that the-shaft 38 which corresponds to the shaft l3 of Figures 1 and 2, is provided with a beveled gear 39 meshing with one face of a double faced bevel gear 40, the other face of the last mentioned bevel gear meshing with a drive pinion M on a worm shaft'fl, which is provided with'a worms-3 meshing with the worm gear3l. It will be readily seen that by rotation of the shaft '38 the worm gear '31 is operated through the intermediate mechanism, so as to rotate the drive'gear 35,and thereby effect simultaneous rotation of the screw shafts. The effect of such rotation is to cause the head 30 to reciprocate longitudinally within the barrel GB, the direction of movement being determined by the direction of rotation of the shaft -38. In a similar manner, the other bladeis moved inwardly or outwardly by meansof the shaft 44 which corresponds to the shaft M of -Figures 1 and2. As illustrated in Figure 5, the shaft 44 is provided with a bevel gear 39a meshing with a double faced bevel gear lla arranged to drive the worm shaft43a. The rest of the mechanism is a duplicate of that already described and therefore is not shown in detail.

In order to effect rotative adjustments of the blades, the inner tubular end of each blade carries a bevel gear 45 which meshes with one face of a double faced bevel gear :46, driven by a .by all of the 4 pinion 41 slidingly mounted on a shaft 48 and engaging the other face of said gear 46. The pinion 41 is connected with the slidable head so as to travel therewith along the shaft 43, the latter being of angular cross'section so as to permit of the sliding movement of the pinion, and at the same time insure its rotation. The shaft 48 is driven by a small countershaft 49 having a bevel pinion 59 meshing with a complemental bevel pinion 5| on the said shaft 4'8. The other end of the countershaft is provided with a bevel pinion 52 meshin with a complemental bevel pinion 53 carried by one end of the shaft 53, the other end of which is provided with a bevel pinion 26 meshing with the pinion 25 driven by the motor R. The mechanism for adjusting the pitch of the other blade, is identical with that already described and is not shown in detail. It is located at the other end of the guide barrel and operated by a shaft 54aprovided with a pinion 21 meshing with gear 25.

In operation, the arrangements of the shafting .and gearing between the motors R. and R are such that the propeller blades will be normally held m ny of the adjusted positions which they are capable of assuming. Energization of the motor R will effect concurrent rotation of the shafts 38 and 44, thereby simultaneously rotating the worm gears 31 and the drive gears .35, where" screw shafts 3! will be rotated in ufiison. As shown in Figures 4, 5 and 6, the two blades are arranged to overlap, so as to reduce the required over-all length of the guide barrel,

and both blades will move inwardly or outwardly according to the direction of rotation of the motor R.

If a change of the effective propeller pitch is desired, the motor B is energized, which through gear 25, pinionsZE and 2'! and the shafts 54 and 54a, and transmission elements actuated thereby, imparts rotative movement to each of the propeller blades within their respective bearings 33, so that the effective pitch presented for action upon the air may be varied as conditions may require.

In the form of the invention illustrated in Figure 7, two propeller blades B are arranged in axial alignment in each guide barrel, there being two operating screw shafts, one for each blade. For instance, a screw shaft 55 for axially adjusting a blade F is mounted in suitable bearings 5511 within each guide barrel GB and is provided with a worm gear 56 which is operated by a shaft 51 which functions the same as the shaft 53 of Figures 1 and 2, Only one screw shaft is illustrated in detail, it being understood that the complemental blade in each guide barrel is actuated by a similar shaft through the medium of a worm gear 56a operated by a shaft 51a which corresponds to shaft M of Figure 1. It will be observed that each of the screw shafts 55 is provided with axially aligned oppositely threaded shanks. Each end of each screw shaft 55 is engaged with the internally threaded portion of slidable heads 58, the inner ends of the propeller blades being secured to bearings 59 rotatively mounted within said heads. The arrangement is such that as the screw shaft 51 is rotated, the heads 58 will be moved inwardly toward each other or outwardly away from each other, depending upon the direction of rotation of the shafts 51 and 51a. The rotative adjustment of the blades is accomplished by means of the motor R with its bevel gear 25 engaging bevel pinions 26 and 21 mounted on tubular shafts 60, 6|. Said shafts are anchored to the respective bearings 59, so that upon rotation of the motor shaft r, the propeller blades will be simultaneously rotated to change the effective propeller pitch, to a degree depending upon the direction of rotation of said shafts.

The actuating structure shown in Figure 8 is exactly the same as in Figure 7, except that it is applied to a two blade propeller.

The advantages of the invention will be readily understood by those skilled in the art to which it belongs. It will be particularly observed that a very simple, easily controlled and operated means is provided for quickly and effectively varying the effective blade length, as conditions may require. Also that equally simple and effective means is provided to quickly adjust the efiective pitch of the propeller blades to promptly meet variations in flight conditions where such adjustment is necessary or desirable. It will be particularly understood that an improved propeller is provided which during flight of the airplane, will be capable of taking full advantage of stratosphere flying without sacrifice of performance at lower altitudes, combined with an increase of thrust at take-off, climbing after take-off, and at high altitudes in level flight.

Having thus explained the nature of the invention and described an operative manner of constructingand using the same, although without attempting to set forth all of the forms in which it may be made, or all of the forms of its use, what is claimed is:

An airplane propeller comprising a housing REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,205,835 Landrum June 25, 1940 2,282,077 Moore May 5, 1942 2,145,413 Belfield Jan. 31, 1939 1,077,187 Bissell Oct. 28, 1913 1,828,303 Turnbull Oct. 20,1931 1,957,887 Hebbard May 8, 1934 2,146,481 Manning Feb. 7, 1939 1,461,733 Hawes July 17, 1923 1,754,192 VanVliet Apr. 8, 1930 2,041,611 Kotelevtseff May 19, 1936 1,915,465 Kohlstedt June 27, 1933 2,404,290 Hoover July 16, 1946 

